1. Field of the Invention
This invention relates to a multi-channel recording apparatus and more particularly to a recording apparatus which is capable of recording data in each of a plurality of areas longitudinally extending on a tape shaped recording medium.
2. Description of the Related Art
During recent years, research and development efforts in the field of magnetic recording have come to be made to increase recording density. As a result, there has been developed a method of digitally recording an audio signal which is compressed in the directions of amplitude and time base. For example, in the case of a magnetic recording and/or reproducing apparatus (hereinafter referred to as VTR) of the two-rotary-head scanning type, the conventional arrangement to have a magnetic tape wrapped at least 180 degrees around a rotary cylinder has been changed to have the tape wrapped around the cylinder to a greater degree (180.degree.+.zeta..degree.) and to record, within an extra wrapped portion of the tape thus obtained, an audio signal which is pulse code modulated (hereinafter referred to as PCM) and time-base compressed.
FIG. 1 of the accompanying drawings shows the tape transport system of the VTR of the above stated kind. FIG. 2 shows recording tracks formed on the magnetic tape by the VTR of FIG. 1. Referring to FIGS. 1 and 2, the illustrations include a magnetic tape 1; a rotary cylinder 2; heads 3 and 4 which are mounted on the rotary cylinder 2 at a phase difference of 180 degrees and have azimuth angles different from each other; an area 5 in which a video signal is recorded within each of the recording tracks (hereinafter referred to as a video recording area); and another area 6 in which an audio signal is recorded within each of the recording tracks (hereinafter referred to as an audio area). The video area 5 corresponds to the 180.degree. wrapped tape portion traced by the heads 3 and 4 while the audio area 6 corresponds to the .theta..degree. wrapped tape portion traced by the heads 3 and 4.
Meanwhile, there is another known method for high density recording, whereby: The VTR of the above stated kind is arranged to have an audio signal which differs from the audio signal recorded in the audio area also recorded in the video area 5. For example, with the angle .theta..degree. assumed to be 36.degree., five more audio areas which are similar to the audio area 6 are obtainable on the tape with the head allowed to rotate to the degree of 5 .theta.=180 degrees. Then, different audio signals can be discretely recorded in these different audio areas respectively in a PCM state.
FIG. 3 shows the tape transport system of a PCM (pulse code modulated) audio signal recording and/or reproducing apparatus of the above stated kind. FIG. 4 shows recording tracks formed on the tape by the apparatus of FIG. 3. Referring to FIG. 4, reference symbols CH1 to CH6 denote six channel areas. Each of the different channel areas CH1 to CH6 consists of an aggregation of tape portions traced by the heads 3 and 4 at the same rotation angle of the rotary cylinder 2. In cases where the audio signal is to be recorded on a tape in a PCM state, the audio signal undergoes a non-linear compressing process while the signal is in the stage of an analog signal. After that, the compressed audio signal has its frequency band limited by a low-pass filter to 0 to 1/2 fs (fs: a sampling frequency) before it is converted into digital data of 10 bits by an A/D (analog-to-digital) converter. Following that, the 10-bit data is non-linearly compressed to 8-bit digital data by means of a quantization table or the like. The 8-bit data is then subjected to a series of error correcting processes including an interleave process, CRCC (cyclic redundancy check code) and parity word adding process, etc. The digital data thus processed undergoes a PCM process before recording on the magnetic tape. During reproduction, the PCM audio data which is thus recorded through the above stated processes is taken out by a PLL (phase-locked loop) according to a bit clock signal locked in the data. The data is subjected to an error detecting process which is performed through the CRCC and an error correction process which is performed by means of the parity word. The data is then expanded from 8-bit data to 10-bit data and is converted into an analog signal by a digital-to-analog (hereinafter referred to as D/A) converter. The analog signal thus obtained is analog expanded into an audio signal through a post-filter.
FIG. 5 is a block diagram showing the above stated signal processing operation. Referring to FIG. 5, an amplitude compression circuit 11 is arranged to compress in the direction of amplitude an analog audio signal which comes via an input terminal 10. A low-pass filter (LPF) 12 is a pre-filter which is arranged to limit the frequency band of the analog audio signal. An A/D converter 13 converts the analog audio signal into 10-bit digital data. A data compression circuit 14 compresses the 10-bit data into 8-bit data. A circuit 15 is arranged to add redundant bits such as a CRCC, a parity word, etc. A modulation circuit 16 performs digital modulation. A reference numeral 17 denotes a memory. An ID data generating circuit 30 is arranged to produce, on the basis of the output of a system controller 27, ID data which will be described later. The memory 17 is arranged to receive the redundant bit which is produced from the circuit 15, the ID data which is produced from the circuit 30 and the audio data produced from the data compression circuit 14. At the memory 17, these data are arranged in accordance with a data format which will be described later and are supplied to the modulation circuit 16 at a given timing. The modulation circuit 16 is arranged to digitally modulate the data from the memory 17 into a form suited for magnetic recording and supplies the modulated data to a magnetic recording/reproduction system 18. The system 18 records the data in one of the plurality of areas CH1 to CH6 on the tape in accordance with a recording format which is as shown in FIG. 4. A clock pulse generating part 28 is arranged to generate clock pulses to be used for controlling the operating timing of each applicable part.
The circuits of the reproduction system includes a demodulation circuit 19 which corresponds to the circuit 16 and is arranged to perform digital demodulation; a memory 20; an error detecting, correcting and interpolating circuit 21; a data expansion circuit 22 which is arranged to expand the 8-bit data into 10 bit data; a D/A converter 23; a post-LPF 24; and an amplitude expansion circuit 25 which is arranged to perform analog signal expansion.
At the memory 20, the data which is demodulated by the circuit 19 is restored to the original data arrangement. Meanwhile, the audio data which is error corrected and interpolated by the circuit 21 is supplied to the data expansion circuit 22. The ID data is supplied to the ID data restoration circuit 31. At the ID data restoration circuit 31, the reproduced ID data is brought back to information data similar to the original data and is then supplied to the system controller 27 to determine the control action to be performed by the controller 27.
The following describes an example of data format conventionally used for the apparatus of the above stated kind: FIG. 6 shows the data format for recording data in one track within each recording area. More specifically, FIG. 6 shows by way of example a data format for including PCM audio data corresponding to the audio signal of two channels of 1/60 sec. In the data matrix of FIG. 6, a column SYNC is for synchronizing data; a column ADDRESS for address data; columns P and Q for error correcting redundant data; and a column CRCC for known CRCC check code data. Each of columns D1 and D2 consists of a plurality of columns and includes audio signal information for two channels. Rows b(0) to b(3x-1) denote the rows of the data matrix. Each row forms a data block with data recorded from the left-hand side of the row to the right-hand side thereof as viewed on the drawing. For example, in the row b(0), the data of the column ADDRESS is recorded following the data of the column SYNC and is followed by the data of the columns P, etc. one after another. In the row b(x+1), the data of the column SYNC is recorded after the data of the last column is recorded in the row b(x). Data recording for one track comes to an end with the data of the last column in the row b(3x-1) is recorded. In the first column among the columns D1, six data ID0 to ID5 of the rows b(0), b(1), b(x), b(x+1), b(2x) and b(2x+1) represent additional (auxiliary information) other than the information of the audio signal and hereinafter will be called as ID data.
The details of the data ID0 to ID5 are as shown in Tables 1 and 2. Referring to Tables 1 and 2, data ID0 is mode designation which consists of eight bits and indicates the kinds of information carried by the data ID1 to ID5. The data ID1 to ID4 in each of the modes 1 to 6 indicate information as shown in Table 1.
TABLE 1 ______________________________________ ID data Re- mode ID0 ID1 ID2 ID3 ID4 ID5 marks ______________________________________ 1 1 hr min sec file No. Y counter 2 2 pro. Cut No. min sec Y cut data No. 3 3 year month day day/week Y time 4 4 hr min sec File No. Y time 5 5 pro. hr min sec Y pro. data No. 6 6 Pro. hr min sec Y tape data No. 7 7 X -- -- -- Y new ID ______________________________________
TABLE 2 ______________________________________ Bit No. ID5 (Y) in each mode ID1 (X) in mode 7 ______________________________________ 1 validity validity 2 audio signal form tape travel direction 3 audio signal form next track No. 4 L ch. audio, etc. next track No. 5 R ch. audio, etc. next track No. 6 record beginning part track pitch 7 record end part track pitch 8 dubbing prevention part corresponding to silent part. ______________________________________
In other words, the data ID1 to ID4 show time information as obtained by a tape counter in the mode 1; time information for every cut in the mode 2; present time information in the modes 3 and 4; time information for every program in the mode 5; and in the mode 6 time information obtained from the leader part of each tape.
In Table 1, "pro. No." means a program number, "cut No." a cut number and "file No." a file number. Generally, in the case of a system wherein all data are to be replaced with data of all "0" when any data error occurs, the system is preferably to have the data of all "0" not readily occur. In that case, each data is arranged to have 0 expressed with all "1" , and 1 with 11111110. In Table 1, symbols X and Y respectively denote 8-bit data. Information represented by these data X and Y is as shown in Table 2. The symbol Y indicates the data ID5 in each of the modes 1 to 7. The first bit of the data Y indicates whether the 8-bit data Y is valid or invalid. The second and third bits indicate whether the above stated audio information recorded in two channels is in a monaural-signal or stereo-signal form or the like. The fourth and fifth bits indicate whether audio signal information or some other information is to be recorded in the corresponding parts of the first and second channels. The sixth and seventh bits are arranged to be at "1" at the record beginning part and the record ending part of the audio signal respectively. The eighth bit is arranged to be at "1" in case that dubbing is to be prevented.
Meanwhile the 8-bit data X indicates information related to this invention as shown also in Table 2. The first bit of the data X indicates whether the data X is valid or invalid. In the case of a system arranged to obtain data consisting of all "0" in the event of occurrence of a data error as mentioned in the foregoing, the first bit of the data X is preferably arranged to be at "1" if the data is valid and at "0" is the data is invalid. The second bit of the data X indicates the direction in which the tape is allowed to travel for recording. The third, fourth and fifth bits of the data X indicate one of the areas CH1 to CH6 in which recording is to be performed next time or indicate, for example, that the recording is to be brought to a stop by showing a next track number, etc. The sixth and seventh bits of the data X indicate the track pitch at which the recording tracks mentioned in the foregoing are to be formed. The eighth bit of the data X is arranged to become "1" only at a part corresponding to a silent part for the purpose of facilitating a leader finding operation. For example, if the analog audio signal coming via the input terminal 10 of the recording system shown in FIG. 5 remains at a level close to a zero level over a given period of time, the eighth bit is at "1" for a given period of time, that is, for a given number of recording tracks.
The form of the main information included in the information signal recorded in the manner as described above is distinguishable by the medium of the ID data. The system described is thus arranged to be capable of recording and reproducing, in addition to the audio signal, a video signal, character information, etc. Therefore, information signals of varied kinds can be recorded in varied combinations.
With the conventional apparatus arranged in this manner, however, the ID data which is recorded in each area as an auxiliary information signal is arranged only for the channel in which the area is included. In cases where main information of one and the same kind is recorded in a plurality of areas by simultaneously using a plurality of channels, the ID data becomes inapposite to a reproducing operation on the main information recorded straddling or spreading over the plurality of channels.
The recording process for recording the main information of one and the same kind on the tape straddling a plurality of recording areas, therefore, has been limited to recording the main information of one kind in given areas in accordance with a predetermined rule.